1. Field of the Invention
The present invention relates to a mechanism which opens and closes by drivably rotating a cover member provided on a cartridge. In particular, the present invention relates to a film cartridge door operating mechanism which opens and closes the light lock door (termed "LLD" hereinafter) of an IX240 cartridge film used in an Advanced Photo System.
2. Description of the Related Art
U.S. Pat. No. 5,231,438 discloses an example of a camera equipped with an LLD opening and closing drive mechanism pertaining to a cartridge film akin to a cartridge film used in an Advanced Photo System. Said camera possesses a first latch supported so as to allow sliding, and a second latch (door driver) which has a linkage to an LLD and is supported on the same rotational shaft as an LLD. When said first latch is moved by an external control member, said second latch rotates, and simultaneously, an LLD is driven to open or close.
Since LLD opening and closing is two-way pivoting in this system, a crank mechanism can be employed as the mechanism for instances in which the unidirectional rotation of a motor serves as a drive source. Specifically, the drive mechanism comprises an LLD driver which possesses a pin disposed off-center with respect to a rotational shaft and which serves to open and close the LLD, a crank cam which similarly possesses a pin disposed off-center with respect to a rotational shaft and which is rotatably driven in one direction by the motor, and a crank lever which possesses a hole into which said crank cam pin may rotate freely, and a slot into which said LLD driver pin may slide freely.
In a design such as that described above, however, rotational motion is converted to sliding motion and once again converted to rotational motion, resulting in a poor torque transmission efficiency. In addition, the applied torque required for LLD rotation is substantial, favoring as much separation of the LLD driver pin from its rotational shaft as possible. On the other hand, the LLD must pivot back and forth through approximately 90.degree., which enlarges the stroke of the crank lever and results in a large mechanism.